What Is Carbon Cost?

Here at Cherwell Collective, we talk a great deal about Carbon Cost. It’s a way of accounting for how our choices generate the greenhouse gas emissions contributing to climate change.  It’s such a major concept for us that we capitalise the term!  Nevertheless, Carbon Cost is a relatively new concept that many consumers aren’t familiar with.

What We’ll Cover

In this article, we aim to offer you a primer on what Carbon Cost is and how to use it when making choices in your day-to-day life.  We will talk about:

• How Carbon Cost relates to other costs, including time and money
• Carbon Cost as a way of accounting for greenhouse gas (GHG) emissions
• How do scientists measure emissions, and how can you?
• How we convert emissions to car mile equivalents as a handy metric of Carbon Cost
• How Carbon Cost thinking can help you make planet-friendly choices

Costs Include Time, Money… and Carbon

As workers and consumers, we often think of the use of our time or our money as costs.  A task might cost an hour of our time, or an item might cost £100 of our savings. We’ve all gotten used to thinking about how to allocate our time and money and reduce costs because we would all like to save both!

Related: Read our introduction to climate change and the major categories of greenhouse gas emissions.

To help the planet and avert climate change, we should also consider what things cost in terms of carbon. “Carbon,” in this sense, is the shorthand for any of the greenhouse gasses (carbon dioxide, methane, nitrous oxide, hydrofluorocarbons) that cause climate change. In turn, Carbon Cost refers to the quantity of those emissions created by each of our consumer choices and actions. To help avert climate change, we should all do our best to “save carbon” – in other words, by cutting our Carbon Cost.

Carbon Cost Vs. Carbon Pricing

Carbon Cost differs from carbon pricing, which are mechanisms that attempt to put a monetary price on greenhouse gas emissions.  Consumers sometimes encounter carbon pricing through carbon taxes or an optional carbon offset fee. Meanwhile, companies and governments sometimes trade carbon credits. Those are all forms of carbon pricing that put a value on emissions in pounds, Euros, or dollars. On the other hand, Carbon Cost is concerned with the quantity of emissions, not the market value/price of the emissions.

Our Daily Lives Are Filled With Carbon Costs

Most of our daily consumer choices have some Carbon Cost attached because we generate emissions when we engage in activities or produce goods. However, we often don’t think about these costs in the same way as we might think about the total amout of money or time we are spending.   For example, consider our routine, daily Carbon Costs:

Transport

• Travel generates emissions when fuel is burned.  Even when you walk or ride a bike, the calories of sugar you burn create small amounts of emissions.
• Powered modes of transportation (scooters, e-bikes, cars, trains, planes) generate emissions when fuel is burned in the engines or at power plants to charge the batteries.
• Additional emissions are embedded in the manufacturing of transport equipment (e.g. manufacturing bikes, rail cars, automobiles, planes) and in building the transport infrastructure (e.g. roads, rail lines, airports, etc.).

Food Production

Producing food is the single biggest source of greenhouse gas emissions. Consider a package of beef, which generates carbon dioxide, methane, and nitrous oxide in its production:

• To raise cows, ranchers use huge quantities of feed like corn and soybeans that could otherwise be used as food for humans. All this feed uses fertilizers that release nitrous oxide emissions.
• Cattle (and sheep) are animals called ruminants that constantly release significant amounts of methane gas into the atmosphere from their complex stomach chambers.
• Slaughterhouses, meat packing plants, refrigeration and shipping also add to the Carbon Cost of beef.  Contrary to popular belief, only a tiny part of the food’s Carbon Cost is the distance the food is shipped, compared to all the steps to raise and produce the beef that come prior.

Climate Comfort at Home

• Heating your home or workplace typically generates emissions when fossil fuels are burned in the furnace. 
• Even a home with electric heat has associated emissions from electricity generated at power plants that use fossil fuels, unless your power supplier is 100% renewable.  In turn, air conditioning uses electricity often generated with fossil fuels.
• Improvements in insulation are important because they can protect from heat loss in the winter or overheating in the summer and prevent you from running up Carbon Costs for the sake of comfort.

Fashion/Wardrobe

Every single item you buy, including clothing items, has Carbon Cost embedded in it. Consider a jumper or a pair of trousers:

• Buying a jumper or a pair of trousers represents emissions created by growing and harvesting the cotton, raising the wool, or manufacturing the polyester
• Other steps in the manufacturing process include spinning those fibres into a fabric using powered machines.
• Dyeing fabrics is also uses large volumes of heated water, which generates more emissions.

We calculate Carbon Costs because people have told us they want an easy way to know the lower-carbon alternatives for the products we buy or the activities we do. For instance, driving an electric vehicle typically has a lower Carbon Cost than driving a petrol one.  Eating fish and chips generates fewer emissions than eating a cheeseburger.  Heating your home with an electric heat pump has a lower Carbon Cost than using a gas furnace.  Similarly, buying a jumper made from organic cotton generates a smaller emissions footprint than one made from ordinary cotton.

Related: Read our four part series on The Carbon Cost of Christmas.

Learning about the Carbon Cost of our choices will empower us to lower our environmental impact as individuals, communities, and the whole UK. Part of our mission at Cherwell Collective is to make the Carbon Cost of those daily decisions as easy to understand and to take into account as possible.

A Handy Measure of Carbon Cost is Car-Mile Equivalents

When scientists communicate with each other about greenhouse gas emissions, they usually measure emissions by their mass in grams, kilograms, or tonnes (1,000 kgs) and convert them to something called carbon dioxide equivalents (CO2e).  Those quantities are useful for researchers and policymakers to track and measure climate change, but let’s face it, the mass of a gas is not exactly an intuitive tool for most of us.

Climate organisations have recognised the utility of converting these emissions measurements to something more familiar.  Enter the car mile equivalent, often shortened to “car miles”. The car mile equivalent is how many miles you could drive an average, ordinary car before it would generate the same quantity of emissions as a given activity.

A Cheeseburger in Car Miles

For instance, making a fast-food-style cheeseburger releases 2.14 kg of CO2e, the same emissions as driving the average car in the UK in 2023 for 9.7 miles. You can also say that the cheeseburger has a Carbon Cost of 9.7 car miles. All the steps that go toward raising the cow, making the cheese and the bun, and growing the vegetables generate the same emissions as driving 9.7 miles.

Meanwhile, flying in economy class from London to Mallorca generates 126 kg of CO2e per passenger. That’s the same emissions as driving 572 car miles, so the Carbon Cost of taking the flight is 572 miles.  Using car miles as a metric for Carbon Cost helps make comparisons easier. 

You can compare the Carbon Cost of the flight (572 car miles) with the cheeseburger (9.7 car miles) and realise that the flight has more than 50 times the Carbon Cost of eating a cheeseburger! If you wanted to make a climate difference, you could forgo just a single flight or alternatively cut out one small serving of beef every week for a year.

Another reason we use car miles is to drive home the connection between different types of costs in our lives, namely time, money, and carbon.  Driving a mile costs money for fuel and in the process, releases a car mile worth of Carbon Cost, but it does save time.  Meanwhile, walking the same mile takes more time but saves on Carbon Cost and money.  Other tradeoffs, such as choosing a chicken sandwich over a beef burger, saves on Carbon Cost without costing us more money or time.  Some choices, like wearing a garment for another year before replacing it, will even save you time, money and Carbon Cost!

A Note On How We Calculate Car Miles

In the UK today, cars get roughly 40 miles per gallon (5.9 litres per 100km). This is actually a big improvement over the fuel economy of cars 10 to 20 years ago.  In today’s fleet of cars, driving one mile in the average car generates 221 grams (0.22kg) of CO2e, according to Nimble Fins’ analysis of Department of Transport data.  To calculate the car mile equivalent for any level of emissions, divide the emissions in kg by .221.

Emissions in kg CO2e

__________________        =   Car Mile Equivalent

.221 kg per mile

Because we calculate car miles using the average fuel economy of cars on the road today, the figures actually change slightly over time as cars get more efficient. They also differ from country to country since cars in some countries are more efficient than in others.  These variations in measurements are ok, because you can still use this tool or carbon calculators offered on many websites to compare different options and see which has a higher Carbon Cost.

Carbon Cost Empowers Informed Decision-Making

When you start developing a sense of the Carbon Cost of different activities, you become empowered to make choices that help the planet by reducing associated emissions.  For instance, what about when choosing a source of protein for lunch? 

100-gram Serving of Chicken – 2 Car Miles

100-gram Serving of Cheese – 4 Car Miles

Fast Food Size Hamburger Beef – 8 Car Miles

Unfortunately, products made from red meat such as cows and lamb tend to have much higher Carbon Costs than other animal products.  Reducing your consumption of such foods can have a powerful impact on reducing your own carbon footprint by hundreds or thousands of car miles each year.

Cherwell Collective and Lady Margaret Hall Carbon Cost Pricing Experiment

In February and March of 2024, Cherwell Collective partnered with Lady Margaret Hall (LMH), one of the constituent colleges of Oxford University, to test the impact of using a menu with Carbon Cost pricing. The LMH student canteen offered a menu in which all the menu items were priced based on their Carbon Cost. The exact same menu was then run in a follow-up week using the school’s ordinary pricing.

During the period using Carbon Cost pricing, diners ordered more plant-based meals that have a lower Carbon Cost, and ordered fewer dishes containing meat, compared to the week without Carbon Costed menus. We outline the details of the experiment in a blog post on the topic.

Our Collective Thoughts Offers Carbon Costing Tips

If you’re curious about how to apply Carbon Costing to your everyday activities like buying clothes, choosing transport, or making a meal plan, check out our blog, Our Collective Thoughts. Every month, we share information about how you can use this tool to make planet-friendly choices.